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Comparison of fast and slow synaptic terminals in lobster muscle

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Summary

Synaptic terminals of fast (FCE) and slow (SCE) excitatory neurons were physiologically identified on separate fibres of one muscle, the closer muscle in lobster claws. The innervation by these identified fibers was demonstrated over long distances (7–21 μm) by examining serial thin sections at periodic intervals. The ultrastructure of each type of innervation was consistent both qualitatively and quantitatively in two separate samples. The FCE innervation is relatively simple in having consistently small-diameter terminals each forming a single long synapse, with few synaptic vesicles, and little if any postsynaptic apparatus. The SCE innervation is more complex in having larger-diameter but more variable terminals forming several short synapses, with many synaptic vesicles and an extensive postsynaptic apparatus. These differences in the size of the synapses and the number of synaptic vesicles parallel differences in transmitter release and fatigue sensitivity characteristic of the two types of innervation. The degree of elaboration of the postsynaptic apparatus may reflect differences in the amount of transmitter taken up after release. Our data reveal for the first time in a single muscle differences between FCE and SCE innervation previously reported in different muscles and in different species.

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Authors and Affiliations

  1. Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts, USA

    R. H. Hill & C. K. Govind

  2. Scarborough College, University of Toronto, West Hill, Ontario, Canada

    R. H. Hill & C. K. Govind

Authors
  1. R. H. Hill
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  2. C. K. Govind
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Additional information

Supported by grants from NIH (NINCDS) to A.G. Humes and the late Fred Lang and from NSERC and Muscular Dystrophy Assoc. of Canada to C.K. Govind

We thank Lena Hill for her technical expertise and critical evaluation of the study, and Dr. A.G. Humes for providing research facilities

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Hill, R.H., Govind, C.K. Comparison of fast and slow synaptic terminals in lobster muscle. Cell Tissue Res. 221, 303–310 (1981). https://doi.org/10.1007/BF00216734

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  • DOI: https://doi.org/10.1007/BF00216734

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